Preparation And Characterization Of Micro/Nanostructured Polyaniline

Properties and applications of materials are not only determined by their composition and structure, but also the size of building blocks and their aggregation state. Due to its variable molecular structures, unique doping mechanism, good redox reversibility, excellent environmental stability, easy preparation and cost-effective raw materials, polyaniline (PANI) has been extensively investigated as an inherent conductive polymer in the last three decades. It is of great theoretical significance to prepare and characterize the PANI micro/nanostructures. This dissertation is focused on the issues of novel methods to prepare PANI with various micro/nanostructures, control their morphologies and size, and self-assembly of the nano-building blocks into hierarchical microstructures. The structures, formation mechanism and the influences of preparation parameters on the PANI micro/nanostructures are also investigated.PANI hierarchical porous microspheres self-assembled from PANI nanowires are prepared from the H2SO4 aqueous solution, which show relatively high conductivity, BET specific surface area and excellent hydrophilic behavior. The results demonstrate that the concentration of aniline, mole ratio of aniline to ammonium peroxydisulfate (APS), polymerization temperature, polymerization time, types of acid and the acidity have significant effect on the morphology of PANI product. The average diameter of the microspheres can be controlled by adjusting the concentration of aniline and polymerization temperature, and the hierarchical microstructures self-assembled from PANI nanowires can be controlled by types of acid and adding sodium dodecylbenzenesulphonate. The uniformity and size distribution of microspheres in the higher concentration of APS can be improved by adding propylene oxide. The oxidant kinds have no obvious effect on the microspheres; however, it will affect the diameter of the microspheres. The formation mechanism of hierarchical microstructures from PANI nanowires is proposed. The Ag-nanoparticle/PANI microcomposite is prepared by combining the self-assembly and in-suit method.High purity, uniformity and crystallinity of PANI nanosheets are prepared from the filtration, which comes from the electropolymerization of aniline. The as-prepared PANI nanosheets are in emeraldine state with the ordered polymer chains and good hydrophobic behavior. The acidity of the electrolyte, electropolymerization time, electrochemical parameters play important role in the formation of PANI nanosheets during the electropolymerization of aniline. The shapes and the lateral sizes of the nanosheets can be adjusted by the acidity of the electrolyte, polymerization temperature and time. A mechanism based on the self-assembly and oriented growth of aniline oligomers is proprosed for the formation of PANI nanosheets, and the higher crystallinity PANI nanosheets are synthesized from the analogue electrolyte prepared by using the H2O2 as oxidant. Meanwhile, it provides the guideline for the re-use of electrolyte of electropolymerization of aniline.The template-free self-assembly of PANI micro/nanostructures provides novel insight into preparation of other polymer micro/nanostructured materials. The PANI hierarchical porous microspheres and PANI nanosheets might have promising applications in the filed of sensor, catalysis support, solid separation and anti-corrosion, self-clean surface, respectively.